Silver salt diffusion process

ABSTRACT

THE IMAGE TONE OF SILVER IMAGES PRODUCED BY THE SILVER SLAT DIFFUSION PROCESS IS UNPROVED BY PERFORMING THE DEVELOPMENT IN THE PRESENCE OF XXXXXXRIAZINE BLUE TONERS.

United States Patent 3,671,242 SILVER SALT DIFFUSION PROCESS Werner Liebe, Siegfried Petersen, and Anita von Konig,

Leverkusen, Germany, assignors to Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany No Drawing. Filed Dec. 30, 1969, Ser. No. 889,352 Claims priority, application Germany, Jan. 25, 1969, D 19 03 741.3 Int. Cl. G03c 5/54 US. CI. 96-29 2 Claims ABSTRACT OF THE DISCLOSURE The image tone of silver images produced by the silver salt diffusion process is unproved by performing the development in the presence of 1,2,4-triazine blue toners.

The invention relates to an improvement in the silver salt diffusion process in which the exposed silver halide emulsion layer is developed in the presence of 1,2,4- triazines as blue toners.

It is already known that the production of an image in the reception layer is advantageously accomplished in the presence of components which influence the color of the silver precipitated in the reception layer. Such compounds form silver salts difficulty-soluble in water and in the sodium thiosulfate solution. Some efficacy is, for example, shown by the compounds described in German Pat. No. 473,000 and 890,755.

These compounds have, however, several disadvantages. In particular they retard the formation of the positive image in the silver salt diffusion process, so that longer contact times are necessary. It is, however, desirable to reduce the necessary copying times, and so need exists for compounds which accelerate the diffusion process and the image formation in the positive material and simultaneously produce, as far as possible, a deep black silver image.

Although the mercapto triazoles described in U.S.-specification 3,307,944 satisfy the practical requirements as regards their blue toner effect and, furthermore, do not retard the diffusion of silver halide, they are unsatisfactory in cases where several positive copies are to be produced from one exposed negative. In such cases it is found that in the presence of these mercapto triazoles the second copy has insufficient covering.

It is among the objects of the invention to improve the silver salt diffusion process so that several positive copies of higher density and with a neutral black image tone can be obtained from one exposed negative.

We now have found a silver salt diffusion process comprising the steps of exposing a supported silver halide emulsion layer, developing the exposed layer in the presence of solvents for the silver halide and in contact with a reception sheet containing development nuclei for the transferred silver halide, wherein the development is performed in the presence of 1,2,4-triazine blue-toners of the following formula:

wherein represents:

The following are examples of compounds which have proved to be suitable 2. (IJOOC2H J-SH 4. (JO-CH3 \NH La The 1,2,4-triazine toners may be prepared by known processes, for example by those described in German patent specification \(P 1 670 979.8).

The compounds are preferably added in quantities of 1 to 200 mg. per m? of image receiving layer and/or similar quantities per liter of developer. Most of the compounds are easily soluble in aqueous alkaline solution and can therefore be added to the known developers for the silver salt diffusion process without the need for changing the formulation of the devoloper. As additives for the alkaline developer solution are preferred 1,2,4- triazines with free mercapto group since these compounds are stable in caustic potash solution. Their activity is only slightly affected by the development temperature but development is preferably carried out at temperatures of between 15 and 35 C.

EXAMPLE 1 Preparation of the reception layer A baryta coating is applied to a support of paper (80 g. per m?) using the following solution:

6 g. of a 50% aqueous slurry of barium sulfate 20 ml. of a10% aqueous gelatin solution 8 ml. of a 50% aqueous emulsion of polyvinyl acetate water up to 100 ml.

The baryta layer is dried and then coated with a nucleated layer using the following casting solution:

4.5 g. of propylene glycol alginate 12.5 mg. of silver sulfide in the form of an aqueous colloidal solution 20 ml. of a 50% aqueous gelatin solution 1.5 ml. of a 30% aqueous solution of potassium bromide 1.2 ml. of a 30% aqueous solution of saponin 7.5 g. of sodium thiosulfate made up with water to Four portions of the above composition are prepared and a certain quantity of one of the 1,2,4-triazine blue toners is added to each of these portions before casting.

Sample .1: Addition of 0.1 g. of compound 1.

Sample 2: Addition of 0.05 g. of compound 2.

Sample 3: Addition of 0.02 g. of compound 5.

Sample 4: Addition of 0.15 g. of compound 6.

The layer is applied in such a thickness that. it contains approximately 1.1 g. of sodium thiosulfate per m.

Another layer of the following casting solution is applied to the layer described above:

3.5 g. of sodium alginate 1 g. of sodium thiosulfate 0.8 m1. of a 30% aqueous potassium bromide solution 8 ml. of a 30% aqueous saponin solution made up with water to 350 ml.

This layer is applied in such thickness that it contains about 0. 6 g. of sodium thiosulfate per m.

Processing The above reception layer is brought into contact with an exposed silver chloride emulsion layer and developed in the following developer bath in a conventional processing apparatus:

G. Sodium sulfite anhydrous 60 Hydroquinone 14 1-phenyl-3-pyrazolidone 1.2 Sodium hydroxide vl1 Potassium bromide 2 Water up to 1 1.

After production of the first copy, the process is repeated so that a second copy is also obtained.

The copies obtained have an excellent neutral black image tone after the usual contact times of about to seconds. The second copy is also in all cases of good quality.

If the process is carried out in the same way but using a mercapto triazole blue toner described in U .8. Pat. No. 3,307,944 in the reception layer instead of the 1,2,4-triazines according to the invention, a first copy of excellent quality is obtained but the second copy has insuflicient covering.

EXAMPLE 2 An exposed silver chloride emulsion layer on a paper support is brought into contact with the reception layer described in Example 1 with the exception that the reception layer does not contain any blue toner.

Development is carried out with the following bath in a conventional processing apparatus:

G. Sodium sulfite Hydroquinone 2 '15 1-phenyl-3-pyrazolidone 1.2 Sodium hydroxide 12 1,2,4-triazine blue toner 0.04

The following compounds are tested:

Sample 1: Addition of Compound 5 to the developer.

Sample 2: Addition of Compound 1 to the developer.

Using a contact time of 5 to 10 seconds, first and second copies with good neutral black tones are obtained. Without the addition of blue toner to the developer, the copies are brown in color. When using a blue toner of the type described in US. Pat. No. 3,307,944 the second copy is unsatisfactory in quality.

l-What is claimed is:

1. In a silver salt diffusion process for producing a plurality of copies from an exposed silver halide emulsion comprising the steps of exposing a supported silver halide emulsion layer and developing the exposed layer in the presence of a silver halide solvent while in contact with a reception layer containing development nuclei for silver halide, the improvement consisting of developing in effective contact with a 1,2,4-triazine blue toner of the following formulae:

wherein represents:

References Cited UNITED STATES PATENTS 3/ 1967 Weyde et al. 9 6- 66 3/1969 Willems et al. 9652 NORMAN G. TORCHIN, Primary Examiner J. L. GOO-DROW, Assistant Examiner US. Cl. X.R. 9-6-5 8 Patent No. 3,671,242 Dated June 20, 1972 Werner Liebe et a1 Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Eolumn 2, compound number 3, should read as follows:

WQ i H N -SH Golumn olaim l, formula 3 should read as follows:

Column 4, claim 2, the formula should read as follows:

NH NM L Signed and sealed this 29th day of May 1973 (SEAL) Attest;

EDWARD M.PLETCHE R,JR. ROBERT GOTTSCHAL'K Attesting Officer Commissioner of Patents 

